Connector for reusable pressureresistant blasting cartridges



April 1954 M. M. LILLY ETAL 2,676,542

CONNECTOR FOR REUSABLE PRESSURE-RESISTANT BLASTI'NG CARTRIDGES FiledFeb. 1a, 1953 F .5. g 4 y L [:1 I 5 f) 10 5 4 INVENTORS M.Lilly JameSRS/ed ATTORNEY Patented Apr. 27, 1954 acres-4a eo s eroagoREUSABLE-PRESSIJEE- ,aasismm nrs rme" meanness MichaelsMxEilly;Charleston, .Va.,. andJames iP.,-Swed,..Gibbstnwn, N. J'.,.assignors==torE. 1.51m t p t .Nem ur e fil mnanriiwilminstnn. pel acorporation of Delaware iipplicatibn-Felirnary 18, 1 953, Serial-Nor3-3-7 ,4 62

1.3 .Q e s {The present; invention relates :to.- an improued l;ass emblyqfQl? proyiding. electrical connection -,f r orn:,,a source ofelectricalzzenergy ,tora blasting ,cartridge of. the reusable; pressureresistant tube It is an object of the present invention sto provide animproved assembly for making: el'ectricaL connectionwiththe firing headof; 21.2111188- sure-resistant blasting I tube. A further object istype; 5 to provide an assembly for making electrical The use ,ofreusable pressure-resistant tube connection with: the fi'ring headof-ikapressure -re blastingcai tridgei in mining; operations; is rapidlysistant. blasting tube wherein the lead wires: will gaininwideacceptance. Essent-ially:, :the blastnot be. damaged byfragments:resulting from the fi .eartnidges consist ,of .a heavy steeltubular blasting action. Additional objects-:will 1986611 119.bodyclosed at one ,end witha firing head and apparent astheinventioirisifurthendescribeda.

at the other endwith; a: pressurerresponsivedis- We have found that" thef-oregoing obj'ects -may .gakitguige; head;. The head: contains a cenbeattained when we providea socket on --the tra lly positionedelectrodewhich extends intothe head end of a pressure-resistant blastingtubular bod-yandisinsulated from the, remainder cartridge; and a plug ofsuchsize aato formtight ,ottl re. blasting cartridge. Thadischarge headfriction fit with the said socket firmly attached containqaa number ofventing, apertures, usually to the lead wires. The-socket is-centrallyposisloping outwardly toward the firing head end tionedat-the outsideend of the firing heagd and of the cartridga.andivalyingimeans or arupturathe insulated electrode within the firing head ble disc whichwill permit the sudden release of projects centrally into the spacecreated by the gases under high pressure from within the tube. socket.The plug is of greater length than the The tube body contains thegas-producing charge, depth of the socket and is preferably molded whichmay be a substance capable of decomposabout the end of a pair of heavilyinsulated leading into gaseous material upon initiation, or may inwires. The end of the plug opposite the wire, be a liquefied orsolidified form of a normally i. e., the end of the plug which isinserted into gaseous material. A typical charge of the former thesocket, has a peripheral metal sleeve which type contains a largeproportion of ammonium is connected to one of the lead-in wires, and anitrate, and is initiated by means of an electrical transverse slotcontaining a metal liner connectheating element imbedded within thecharge. A ed to the other lead-in wire. The liner is shorter typicalexample of the latter type substance is than the diameter of the plug sothat it is not carbon dioxide solidified or liquefied under presincontact with the sleeve which is also slotted at sure and gasified bythe heat produced by the the same points. When the plug is inserted intoaction of an exothermic starter mixture or by an the socket, the sleeveis in contact with the sides electrical resistance coil. The startermixture is of the socket and the liner is in contact with the initiatedby means of an electric squib or an electrode, thus providing thedesired electrical electric heating element. contacts.

In use, the charged blasting tube is loaded into In order to more fullydescribe the present ina borehole after lead wires have been connectedvention, reference is made to the accompanying to the firing head, andinitiated by the applicadrawings, in which: tion of current through thelead wires. Due to Figure 1 represents a plan view of the blasting theshattering action of the suddenly released assembly i accordance t tpresent, inven gases, the entire assembly is frequently buried tion;under a mass Of broken fragments. Since the Figure 2 represents apartially sectional view of fragments have sharp edges and strike theasth assembly; sembly with considerable force, the lead wires Figure 3represents a view of the plug from the are naturally subjected to severeabuse. Atonta t end; d tempts have been made to pr v de permanent Figure4 represents a View of the plug from the connections where the leadwires were heavily side. shielded and firmly secured to the firing head.Referring to the figures in greater detail, I is a This assembly is bothclostly to produce and tube body, generally of steel, of thepressure-redifiicult to repair. Another practice has been sistantcartridge, 2 is the discharge head which to use expendable wire at theportion near the contains the pressure-responsive release mechatube. Thedisadvantages of this practice are nism and the venting ports, 3 is thefiring head, the time required for repeated connections, the 4 is theplug at the end of the insulated leadloss of wire, and the contaminationof the matein wires, 5, 6, and I representing the individual rial beingblasted. lead-in wire cores. 8 is a U-shaped metal liner inserted inslot I0 transversely across plug 4. 9 is a metal sleeve surrounding theslotted end of plug 4, being itself slotted in alignment with slot I 0.H is an electrode inside and insulated from firing head 3 by insulatorsI2, the latter being retained in position by element 13.

As is-shown in the drawings, lead-in wire core 6 is welded to sleeve 9while lead-in wire core 1 is welded to line 8. When the plug is in theposition shown in Figure 2, the sleeve 9 forms electrical contact withthe firing head 3 and liner 8 forms electrical contact with theelectrode II. In the preferred form of the invention, sleeve 9 will beforced inwardly on plug 4 by the insertion in the socket in firing head3, and liner 8 will be expanded by the entrance of electrode l I, sothat the plug 4 will be under compression, thus assuring retention ofthe plug 4 in the socket during the insertion of the assembly into aborehole, and also better electrical contact with the firing head 3 andthe electrode H.

The assembly of the plug and blasting cartridge are secured togetheronly by the friction fit. Thus, when the cartridge is initiated within aborehole an initial stream of gases issue through the space between theborehole and the cartridge outwardly at tremendous velocity. These gaseshave suflicient drag on the plug and lead-in wire to detach the plugfrom the firing head and blow it completely free from the fall of thematerial being blasted. The slot 10 permits shaking out any dirt andfacilitates cleaning liner 8 to insure a good contacting surface, sothat the plug assembly is ready for reuse by simply inserting into thefiring-head socket of a charged blasting cartridge.

The plug is preferably molded directly onto the length of heavilyinsulated lead-in wires,

but clamp or screw connections may be used. Natural or synthetic rubberis the preferred resilient material of a non-conductive nature forfabrication of the plug, but materials such as synthetic polymers havingthe desired resilience may also be used. Accordingly, we intend to belimited only by the following claims:

We claim:

1. An improved blasting assembly of a reusable blasting cartridge of thetype described herein and a detachable lead-in wire device adapted to beblown free and clear of the fall of blasted material by the dischargewithin a borehole of said cartridge which comprises a firing head at theinitiation end of the cartridge containing a central cylindrical socketat the outside end thereof, an insulated electrode in axial alignmentwith said firing head and having one end projecting into said socket,and a cylindrical plug of a resilient non-conductive -material, aportion thereof being inserted in said socket, said portion having ametal sleeve about the periphery in contact with said firing head, atransverse slot across the end of said plug and sleeve containing acentrally positioned metal liner of shorter length than the diameter ofthe plug in contact with said electrode, said plug being secured to twoinsulated lead-in wires, one of which is connected to said metal sleeveand the other to said metal liner, said plug and sleeve forming a tightfit with said socket.

2. An assembly as claimed in claim 1, wherein the sleeve has a normaloutside diameter slightly larger than the diameter of said socket.

3. An assembly as claimed in claim 1, wherein the plug is molded to theinsulated lead-in wires.

No references cited.

